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OCR A Chemistry Paper 2 Unofficial Mark scheme

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Reply 160
Avatar for Thedkk
Thedkk
Original post by Boss987
Acyl chloride. Most reactive right??


I put that too..hope it's right
For the MCQ, if it was a benzene ring then alicyclic and saturated is wrong because each carbon has one delocalised electron so it's not saturated. But it might have been a cycloalkane.
Original post by Ashleigh123456
At the end L was a Ester: CH3CH2COOCH2C(CH3)2CH3
M was a carboxylic acid: CH3CH2COOH
N was an alcohol : HOCH2C(CH3)2CH3

(although i'm pretty sure you could've had the groups the other way around too)


did we also have to find M AND N or just L?
Reply 163
Avatar for Yeahwhat
Yeahwhat
OP
22
Original post by aliyagg98
did we also have to find M AND N or just L?


Just L mate. That guy is on cheese
Guys i bullet pointed the Purity long answer kinda worried now....i kinda learned to bullet point to make examiners life easier whilst reading by work.
Original post by Desmos
For the MCQ, if it was a benzene ring then alicyclic and saturated is wrong because each carbon has one delocalised electron so it's not saturated. But it might have been a cycloalkane.


it was cyclohexane or pentane cant remember
Original post by perupanda
Not sure, but it is definitely important during recrystallisation to use a Büchner funnel as without it it will not filter. Possibly may lose one? But I guess most of the marks were for purity and % yield.


when you use the Buchner funnel did you put wash it with distilled water?
Original post by Boss987
Acyl chloride. Most reactive right??

acyl chloride becuase when it dissolves in water it makes carboxylic acid and hcl therefore most acidic
Reply 168
Avatar for rmpg
rmpg
Original post by Boss987
71% yield.
Did anyone get 95 repeat units?
Ester for hydrogen NMR. This includes 3 CH3.
At the end L was a Ester: CH3CH2COOCH2C(CH3)2CH3
M was a carboxylic acid: CH3CH2COOH
N was an alcohol : HOCH2C(CH3)2CH3 (Ashleigh)
recrystallisation for the method.
Phenol with ethanone joined together. for C NMR.
https://www.thestudentroom.co.uk/attachment.php?attachmentid=665762&d=1497870262
Butan-1-ol + 2O] --> Butanoic acid and Water, using acidified potassium dichromate and under reflux
Butan-1-ol + [O] --> Butanal and water, using acidified potassium dichromate and distillation technique (AnnaRainbows)
Diol more soluble as it has two hydroxyl groups.
Alcohol forms h bonds with water so soluble.
https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=imgres&cd=&cad=rja&uact=8&ved=0ahUKEwiYpraK5snUAhXIRhQKHRq4ApsQjRwIBw&url=https%3A%2F%2Fsites.google.com%2Fsite%2Fchemistryolp%2Fproperties-of-alcohols&psig=AFQjCNE3IJAvXsyhyEHRkFttGAEllLCWZg&ust=1497957876618458
Beta carotene Q
C40H56 + 11H2 --> C40H78 (TuffyandTab)

MCQ
BDCBDCACCBCAACB (tamoni4)
AgNo3
C7H14 - molecular formula
Addition reaction (economy)
Trigonal planar - Atom no. 3
3 peaks for NMR in MCQ
3 or 4 Chiral carbons??
Acyl chloride + primary amine = amide MCQ
Alicyclic and saturated??

Good Paper!!!


Wait did we need to identify M and N in the final Q???
Original post by bethanydewhirst
i did a question in one of the specimen papers and forgot to include a bit of it but because they specifically asked for that bit as well in the question I got no marks even though I wrote about everything else because of the levelled markscheme. Not sure if it'll be the same for this one though, it depends what's required for each level


I swear it said how would you purify and not how would you purify AND check the purity?
it asks *you* to check the purity via % yield so hopefully not putting the melting point check should be ok
Original post by Desmos
For the MCQ, if it was a benzene ring then alicyclic and saturated is wrong because each carbon has one delocalised electron so it's not saturated. But it might have been a cycloalkane.


Unsaturated simply means no double bonds, benzene rings are saturated
Reply 171
Avatar for StA200
StA200
6
Original post by callumabbott99
Unsaturated simply means no double bonds, benzene rings are saturated


Benzene is unsaturdated
Original post by Asiangirl101
Produces 1 water
But 0.1 mole
So it's 6.02 x 10^22


was a diprotic acid with a monobasic base. therefore 1:2, so 0.1mol of NaOH reacts with 0.05 mol acid, and 1 mol of acid forms 1 mol of water, so 0.05mol water forms, which is 0.05*6.02*1023= 3.01*10^22
Original post by callumabbott99
Unsaturated simply means no double bonds, benzene rings are saturated


Benzene is unsaturated, saturation means you can't add any more groups to it. Benzene is C6H6. Cyclohexane is C6H12, so you can add more H's to benzene so it's unsaturated
Original post by aliyagg98
did we also have to find M AND N or just L?

Just to recognise that they were C.acids and alcohols, you didn't need the structure
Reply 175
Avatar for StA200
StA200
6
Original post by Toffo132
was a diprotic acid with a monobasic base. therefore 1:2, so 0.1mol of NaOH reacts with 0.05 mol acid, and 1 mol of acid forms 1 mol of water, so 0.05mol water forms, which is 0.05*6.02*1023= 3.01*10^22


I think it was double that. Somebody explained it before but I can't rememberer where now hahahah

Basically, because 0.1 mole of the acid reacted with 0.1 mol of NaOH, the acid was a limiting reagent so not all of it reacted. But all of the NaOH would so it was 0.1 mol of NaOH equal and 0.1 mol of water
(edited 6 years ago)
Original post by Sam Mccready
when it had the question about hydrogenation of the cyanide I put H2 as a reagent but not nickel, would you need nickel? or am i completely wrong?


you need the nickle, RCN doesnt readily react with H2, much like C=C
Original post by thursdaygirl
Was it correct to put H2 and nickel for BOTH times it asked something about reduction (think one of them was a benzene ring with a ketone group on it?).

I started getting confused about potentially using LiAlH4, but put H2 and nickel twice to be safe

edit: think i remember the Qs. One involved CN and one was benzene with one ketone group. put H2 and nickel for both, but were they trying to trick us? Does one not work with H2/nickel?


For a benzene ring you need Tin(Sn) and Conc. HCl
Original post by medhelp
I swear it said how would you purify and not how would you purify AND check the purity?
it asks *you* to check the purity via % yield so hopefully not putting the melting point check should be ok


maybe, I can't really remember 100% but i'm pretty sure it did ask for both. you should check with your teacher when they see the paper
Original post by Toffo132
Yes, 0.1 Mol NaOh would react, and the eqn would be
(not sure if it's this exact acid but doesnt matter)
HOOCCOOH + 2NaOH -> H2O + NaOOCCOONa
so 2 mols of NaOH forms 1 mol of water,
so 0.1mol NaOH forms 0.05 mol water
0.05*6.02*10^23
=3.01*10^22


That equation is not balanced, should be 2H2O

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